Display screen or portion thereof with a graphical user interface



FIG. 1 is a front view of a first embodiment of a display screen or portion thereof with a graphical user interface showing our new design; and,

FIG. 2 is a front view of a second embodiment thereof.

The heavy broken lines shown as part of the icons in the upper right form part of the claimed design. The longer broken line showing of a display screen and the fine broken line showing of a graphical user interface are included for the purpose of showing portions of the article which form no part of the claim. 

CLAIM We claim the ornamental design for a display screen or portion thereof with a graphical user interface, as shown and described. 